REQUIRED EOR THE ATTACK OP A MODERN PORTRESS. 
97 
curved fire impossible,* * * § nor yet even more difficult than by direct fire 
from the crowning; for, if the requisite final velocity cannot be 
obtained by increasing the rangef to the effective limit, it may be by 
diminishing the required angle of descent, either by firing at the 
covering work or by mining it; J a labour which would equally have to 
be gone through in the case of direct fire from the crowning. 
(See Plate i. fig. 1.) 
Curved fire being, therefore, employed in breaching and in similar 
work, such as the demolition of casemated flanking works, the ordnance 
employed in the first artillery position || for this nature of fire are 
equally suited for it in the second; it becomes merely a question 
whether the heavy or the light nature is best for the purpose. To 
throw light upon this we may refer to the experience of the Franco- 
German war of 1870, that, “the short 15 c.m. gun had taken four 
firing days (about 48 hours) of indirect fire for the establishment of a 
breach at Strasburg; a length of time which, in many cases, would 
have to be curtailed, and which only could be done by the employment 
of a larger calibre/' And, again, to the results of the Graudenz 
experiments, that “a comparison of the effect of the short 15 c.m. and 
21 c.m. gun§ shews, that, with the same striking velocity, an equal 
weight of projectiles was required to produce equal results. The 
advantage of the heavy calibre is not therefore to be sought in the use 
of less ammunition, but in other factors; these are time and accuracy. A 
reduction in time for breaching will always be important and necessary, 
if only with reference to the suitable combination of this mode of firing 
with the works of the engineers."** To this we may add that, for a given 
high angle of descent, the requisite final velocity will more readily be 
obtained from the heavier than from the lighter nature, for the former 
will perform the same work as the latter with a much less final 
velocity, even allowing for the greater resistance of the masonry due 
* If, however, in works of the future, the escarp or work to be demolished is protected 
by armour plates, direct fire must be employed to pierce and loosen them, and the 
besiegers will have to place in battery, by mechanical means, pieces of far heavier nature 
than now in use. 
f Nothing is gained in reducing the angle of descent by making the line of fire oblique, 
for example; the Austrian short 15 c.m. gun, at a range of 1640 yds. with charge of P54 
lbs., at an angle of descent of 22° 7 1 , has a final normal energy of 172,200 ft. lbs., but, 
if the angle of descent be reduced to 15° 5o' by making the line of fire 46 g oblique, at the 
same range, with charge of 1*98 lbs. the final normal energy is only 118,600 ft. lbs. 
If, however the angle of descent be kept at 22° 7and the range increased to 2170 yds. 
with charge of 1’98 lbs. the final normal energy will be 216,000 ft. lbs. 
With high angles of descent the point of impact may possibly be taken higher than the 
middle of the escarp, and the requisite angle so reduced ; for, the higher the angle, the 
greater the tendency to cut downwards as well as into the masonry. 
J This no doubt will, in future, be generally necessary, unless pieces of far greater 
power than now in use are introduced into the siege train for breaching and perhaps 
even then. Possibly simple horizontal boring might take the place of mining. 
|| That is for enfilade chiefly. 
§ The 15 c.m. short gun expended 74'5 shots (about 61*1 lbs. the projectile) per metre of 
breach, the 21 c.m. gun 30*4 shots (about 176 0 lbs. the projectile.) 
** Prussian Portress and Siege Artillery, fourth part, by Major H. Muller. 
13 
